# CPU (The Sweat) When Postgres has a `NULL` wait event (or shows active CPU), the elephant isn't trapped or waiting—he is **Sweating**. He is currently using every available neuron to calculate, sort, or hash. This isn't necessarily a "problem" (it means the elephant is working!), but if he stays in this state too long, it means your request is too complex for his brain. ## Where do the cycles go? ### 1. [[TupleProcessing|Tuple Sifting]] Walking through a massive pile of records and deciding which ones to keep. ### 2. [[MemoryAlgorithms|The Desk Juggling]] Performing a [[Sort]] or a [[HashJoin]] entirely in memory. If the data fits on the elephant's desk (`work_mem`), he stays in "The Sweat" mode. ### 3. [[ExpressionEvaluation|The Math Exam]] Calculating complex regular expressions, performing heavy math, or evaluating logic across millions of rows. ### 4. [[Spinning|The Panic]] Sometimes, the elephant is so stressed he just runs in circles for a few milliseconds, waiting for someone else to move (Spinlocks). This is the fastest, "hottest" kind of work. If the elephant is sweating too much, search the [[_Postgres Operations|Operations Plan]] for expensive [[Sort]] or [[SeqScan]] nodes.